1. Field of the Invention
The present invention relates to a monitor for monitoring a state of molding in an injection molding machine.
2. Description of the Related Art
States of various variables such as injecting velocity, injecting pressure, and the like during injection in an injection molding cycle can be regarded as indicators of good or bad of a molding state. Therefore, the various variables during molding are sampled and graphed on a display and molding conditions are adjusted and evaluated and stability of molding is judged based on the graphs. Especially in evaluating the stability of the molding, waveforms are drawn one upon another through a plurality of molding cycles so that how the waveform fluctuates through the respective cycles and cycle-to-cycle variation in the waveform can be grasped.
In order to grasp how the waveform fluctuates and changes through the molding cycles, order of the drawn waveforms of the molding cycles needs to be judged. However, if the waveform graphs are drawn one upon another, the waveforms overlap each other and it becomes difficult to discriminate the changes in waveforms in the molding cycles from each other. Therefore, there is a known method in which the latest waveform graph and preceding waveform graphs are drawn in different colors to discriminate the changes in the waveforms in the molding cycles over time from each other (see Japanese Patent Application Laid-open No. 2-26724, for example).
Moreover, there is also known art in which a shot number (molding cycle number) is designated on a horizontal axis (first axis), an injection start position or an amount of cushion is designated on a vertical axis (second axis), a lot is designated on a third axis, and relative relationships between three kinds of monitoring data are displayed in three dimensions (see Japanese Patent Application Laid-open No. 2002-273773, for example).
In order to judge the stability of the molding state, it is preferable that how the various variables change and vary over time in a single molding cycle can be grasped and also that the changes and variations in the variables in the molding cycles can be observed and discriminated from each other. In other words, it is preferable that changing and varying patterns of the respective variables in the single molding cycle can be grasped and that variations and changes in the patterns in the plurality of molding cycles can be discriminated from each other. In the above-described prior-art method described in the above-mentioned Japanese Patent Application Laid-open No. 2-26724 in which the molding waveform patterns are displayed in different colors, the latest waveform pattern and the past waveform patterns can be discriminated from each other based on the different colors because they are in different colors. However, the past waveform patterns are in the same color and both the past waveform patterns and the latest waveform pattern are drawn one upon another. Therefore, the waveform patterns overlap each other and it is difficult to discriminate variations, changes, and trends in the variations in the waveform patterns from each other.
In the method described in the above-mentioned Japanese Patent Application Laid-Open No. 2002-273773, the waveform patterns in lots can be compared with each other to grasp differences between the lots. However, it is impossible to grasp how the variable varies and how a waveform pattern varies and changes in a single molding cycle and to judge stability of molding.